...and the answer is suggesting OP to have a look at QlikAuthNet but it seems to be based on "ticket authentication". But surely, it must be enough authenticate using Windows authentication as described in the following links below?
Ok. But are you connecting directly to the Engine, or are you going trough the proxy? This error only occurs becuase POSt command have some issues while going trough the proxy. And to go directly, you need the certificates.
Im not programming in C# and i have never done so. Im scripting in a language called autoit and I have only got this to work trough the proxy
Edit: Here is my working code for a standard GET request.
This uses a standard web request with username and password and i query the Proxy, and i get a response.